Comorbidity and its relevance on general hospital based mortality in major depressive disorder: a naturalistic 12-year follow-up in general hospital admissions

Major depressive disorder (MDD) is associated with physical comorbidity, but the risk factors of general hospital-based mortality are unclear. Consequently, we investigated whether the burden of comorbidity and its relevance on in-hospital death differs between patients with and without MDD in a 12-year follow-up in general hospital admissions. During 1 January 2000 and 30 June 2012, 9604 MDD patients were admitted to three General Manchester Hospitals. All comorbidities with a prevalence ≥1% were compared with those of 96,040 age-gender matched hospital controls. Risk factors of in-hospital death were identified using multivariate logistic regression analyses. Crude hospital-based mortality rates within the period under observation were 997/9604 (10.4%) in MDD patients and 8495/96,040 (8.8%) in controls. MDD patients compared to controls had a substantial higher burden of comorbidity. The highest comorbidities included hypertension, asthma, and anxiety disorders. Subsequently, twenty-six other diseases were disproportionally increased, many of them linked to chronic lung diseases and to diabetes. In deceased MDD patients, chronic obstructive pulmonary disease and type-2 diabetes mellitus were the most common comorbidities, contributing to 18.6% and 17.1% of deaths. Furthermore, fifteen physical diseases contributed to in-hospital death in the MDD population. However, there were no significant differences in their impact on mortality compared to controls in multivariate logistic regression analyses. Thus in one of the largest samples of MDD patients in general hospitals, MDD patients have a substantial higher burden of comorbidity compared to controls, but they succumb to the same physical diseases as their age-gender matched peers without MDD.